SPC files are programs. By reverse engineering the SPC files, it would be possible to make a complete version of the intro song without using the one from the demo version. You could hack the SPC to have a timebomb after which it triggers the event on its own. Since it's not actually downloading the new song from the 65816, this should work.
The real reason I'm mentioning this is maybe Frog's Theme has the intro part still in there, just hidden by lack of event.
I know its an old topic but I wanted to explore this further.
B64F3 - Frog's Theme [pre-release]
B340F - Frog's Theme [retail]
The Pre-Release ROM's Frog theme SPC sequence is the exact same as the regular CT rom--as I'm sure by now you know this. I didn't find any additional sequence for the "intro" that is on the Japanese OST in the ROM.
However, you could just recompose the sequence yourself with the intro if you know what notes/channels you'd have to use.
And I'm assuming by "demo rom" you are infact referring to the pre-release rom. If not I'd to konw what you are referring to as "demo rom".
